iptables firewall help

[Matthew Garman <garman@uiuc.edu>]

I would like to upgrade my kernel from 2.2 to 2.4.  The main thing that
concerns me is building a new iptables-based firewall (as opposed to
ipchains).

I was using the TrinityOS firewall for ipchains.  I read through it,
somewhat, but basically accepted its security on blind faith.

I figure that with the switch to 2.4 and iptables, now would be a good
time to really learn how to write a good firewall script.

So for starters, I'd like to have a good, secure, well-commented iptables
firewall script that I could use and learn from.  Then I'd like to see
some online documentation on firewall considerations.

For the summer, I want a firewall that works with dynamic IP addresses so
my dad and I can share a modem (standard, ultra-slow serial analog modem),
running no services.

Then, when I go back to school, I'll want to change the script so I can
share a cablemodem with my roommates.  I'll also run a couple basic
services at that time, such as a mailer, an SSH daemon, and probably
Apache.

If anyone can point me in the right direction to get started, I would be
very appreciative :)

Thanks!
Matt

-- 
Matt Garman, garman@uiuc.edu
"I'll tip my hat to the new constitution, Take a bow for the new revolution
 Smile and grin at the change all around, Pick up my guitar and play
 Just like yesterday, Then I'll get on my knees and pray..."
            -- Pete Townshend/The Who, "Won't Get Fooled Again"